[mipsel+rs780e]Occasionally "GPU lockup" after resuming from suspend.

[Chen Jie]

在 2012年2月17日 上午12:32，Jerome Glisse <j.glisse at gmail.com> 写道：
> Ok let's start from the begining, i convince it's related to GPU
> memory controller failing to full fill some request that hit system
> memory. So in another mail you wrote :
>
>> BTW, I found radeon_gart_bind() will call pci_map_page(), it hooks
>> to swiotlb_map_page on our platform, which seems allocates and returns
>> dma_addr_t of a new page from pool if not meet dma_mask. Seems a bug, since
>> the BO backed by one set of pages, but mapped to GART was another set of
>> pages?
>
> Is this still the case ? As this is obviously wrong, we fixed that
> recently. What drm code are you using. rs780 dma mask is something
> like 40bits iirc so you should never have issue on your system with
> 1G of memory right ?
Right.

>
> If you have an iommu what happens on resume ? Are all page previously
> mapped with pci map page still valid ?
The physical address is directly mapped to bus address, so iommu do
nothing on resume, the pages should be valid?

>
> One good way to test gart is to go over GPU gart table and write a
> dword using the GPU at end of each page something like 0xCAFEDEAD
> or somevalue that is unlikely to be already set. And then go over
> all the page and check that GPU write succeed. Abusing the scratch
> register write back feature is the easiest way to try that.
I'm planning to add a GART table check procedure when resume, which
will go over GPU gart table:
1. read(backup) a dword at end of each GPU page
2. write a mark by GPU and check it
3. restore the original dword

Hopefully, this can do some help.